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Biomedical subjects

M Richter

Publications and source records attributed to M Richter.

At least 145 records · Page 8Linked to original sources
PubMed1999

[Acceleration injuries of the cervical spine in seat-belted automobile drivers. Determination of the trauma mechanism and severity of injury].

The analysis of 1,176 whiplash-type neck distortions was sought from a total of 3,838 restrained car driver incident reports. The percentage of these injuries increased from less than 10% in 1985 to over 30% in 1997. These occurred mostly with head-on or with multiple collisions, and only in 15% with pure rear-end collisions. In 23.2%, delta v amounted 10 km/h or less, which corresponds to a very minor crash. The average delta v was the highest in the cases of head-on collisions. Letters were sent to the injured to find out about the duration and type of complaints caused by a cervical spine injury. Of the 138 patients who returned the questionnaires, 121 (88%) indicated that they had or were still suffering from their symptoms. Percentage of various complaints were as follows: pain (74%), tension (6%) and stiffness (5%) in the head (27%), neck (55%) and shoulder (8%). The duration of the complaints was longest after multiple collisions and when the onset of complaints was later than 24 hours after trauma. Women and elderly persons predominated slightly in the group with longer duration of complaints. A correlation between the severity of the accompanying injuries and duration of complaints occurred. Also, with this retrospective study there was considerable difficulties in the lack of adequate follow-up for these patients with less severe injuries. In order to better evaluate this problem, prospective studies are necessary which include documentation of diagnosis, treatment protocols, duration and type of complaints.

Acceleration↗
PubMed1999

A complication of intraoperative facial nerve monitoring: facial skin burns.

OBJECTIVE: To report on three cases of severe facial skin burns resulting from intraoperative facial nerve monitoring in patients undergoing parotidectomies. STUDY DESIGN: This study is a retrospective case review. SETTING: A tertiary referral center. PATIENTS: This study includes three patients who underwent parotidectomies with concurrent facial nerve monitoring. RESULTS: Facial skin burns were proven to result from a technical defect of the intraoperative facial nerve monitoring device. Burns were sustained at electrode insertion sites and their extent was related to the duration of monitoring. The most probable explanation of these burns is electrolysis. CONCLUSIONS: Successful retracing of technical defaults with biomedical engineers at the device manufacturer have led to the upgrade of the facial nerve monitor apparatus. The benefits of facial nerve monitoring largely outweigh the fortuitous occurrence of skin burns reported in this study. Therefore, this complication should not represent a drawback to the use of facial nerve monitoring.

Adult↗
PubMed1999

Upper airway compression after arthroscopy of the temporomandibular joint.

An unusual complication is presented following a temporomandibular arthroscopy carried out under general anaesthesia. Severe cervicofacial oedema occurred immediately after surgery which required prolonged endotracheal intubation. Retrospective analysis revealed a massive fluid escape in the surrounding tissues leading to laryngeal oedema.

Airway Obstruction↗
PubMed1998

High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory.

State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few micro W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500 eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples.

Journal Article↗
PubMed1998

Dose variation at bone/titanium interfaces using titanium hollow screw osseointegrating reconstruction plates.

PURPOSE: To evaluate dose variations at bone/titanium interfaces in an experimental model designed to simulate postoperative radiotherapy in patients with mandibular reconstructions using a titanium hollow-screw osseointegrating reconstruction plate (THORP) system. MATERIALS AND METHODS: The model consisted of a 25 x 25 x 10 mm3 block of fresh bovine femoral diaphysis, to the surface of which a segment of THORP system reconstruction plate was fixed by means of a solid titanium screw 4 mm in diameter and 10 mm in length. Using specially designed thermoluminescent dosimeters (TLD) 2 mm in diameter and 0.13 mm in thickness, dose measurements were carried out at four distances from the screw axis (0.1, 0.3, 0.6, and 1 mm). 60Co and 6-MV photon beams were used at incidences both perpendicular and parallel ("axial") to the screw axis. RESULTS: For 6-MV X-ray beams incident perpendicular to the screw axis, the maximum dose enhancement (due to backscatter) and the maximum dose reduction (due to attenuation) at the bone/titanium interface were 5% (+/- 2%) and 6% (+/- 2%), respectively. The corresponding values for 60Co beams were 6% (+/- 5%) and 10% (+/- 5%). For the axial incidences, a maximum dose enhancement of 5-7% was noted for both 6-MV X-rays and 60Co for beams incident on the surface containing the THORP plate segment, whereas beams incident on the opposite surface induced only a very small dose enhancement (2-3%). CONCLUSION: Using a new experimental model, TLD measurements showed only marginally significant dose variations at bone/titanium interfaces around THORP screws, all measured values being very close to the uncertainty limits (+/- 5%) associated with the method. For both 60Co and 6-MV beams, dose variations appeared smaller for axial than for perpendicular incidences. Because photon beams used in head and neck cancer treatment are most often directed parallel to the screw axes, these results suggest that failures of prosthetic osseointegration are unlikely to be explained by an overdosage at the bone/titanium interface.

Animals↗
PubMed1998

Adenosine A2A receptors inhibit the conductance of NMDA receptor channels in rat neostriatal neurons.

Whole-cell patch clamp experiments were carried out in rat striatal brain slices. In a subset of striatal neurons (70-80%), NMDA-induced inward currents were inhibited by the adenosine A2A receptor selective agonist CGS 21680. The non-selective adenosine receptor antagonist 8-(p-sulphophenyl)-theophylline and the A2A receptor selective antagonist 8-(3-chlorostyryl)caffeine abolished the inhibitory action of CGS 21680. Intracellular GDP-beta-S, which is known to prevent G protein-mediated reactions, also eliminated the effect of CGS 21680. Extracellular dibutyryl cAMP, a membrane permeable analogue of cAMP, and intracellular Sp-cAMPS, an activator of cAMP-dependent protein kinases (PKA), both abolished the CGS 21680-induced inhibition. By contrast, Rp-cAMPS and PKI 14-24 amide, two inhibitors of PKA had no effect. Intracellular U-73122 (a phospholipase C inhibitor) and heparin (an inositoltriphosphate antagonist) prevented the effect of CGS 21680. Finally, a more efficient buffering of intracellular Ca2+ by a substitution of EGTA (11 mM) by BAPTA (5.5 mM) acted like U-73122 or heparin. Hence, A2A receptors appear to negatively modulate NMDA receptor channel conductance via the phospholipase C/inositoltriphosphate/Ca2+ pathway rather than the adenylate cyclase/PKA pathway.

Adenosine↗
PubMed1998

Human immunodeficiency virus activity in rib allografts.

PURPOSE: The use of bone allografts involves the risk of transmitting infectious agents from the donor to the recipient as shown by historical surveys. A study was therefore undertaken to test the hypothesis that human immunodeficiency virus (HIV) activity can still be present after the freezing and thawing of ribs taken from an acquired immune deficiency syndrome (AIDS) patient at autopsy. MATERIALS AND METHODS: Rib samples were harvested under sterile conditions and frozen at -80 degrees C. After different freezing periods, the samples were cultured with activated lymphocytes. P24 antigen determination in the supernatant fluid was used to test for viral activity. RESULTS: Confirmation of viral activity was obtained after freezing periods ranging from 1 to 12 weeks. CONCLUSIONS: HIV activity can be found in ribs of AIDS patients, and this outlives the cryoprotection of bone banking. Donor selection remains the main security in the use of frozen bone allografts.

Adult↗
PubMed1998

Effect of anthraquinone-laxatives on the proliferation and urokinase secretion of normal, premalignant and malignant colonic epithelial cells.

Even though 1,8-dihydroxyanthraquinone (DHA)-laxatives have been implicated in colon carcinogenesis, the available information is still inconclusive. The aim of this study was to demonstrate the effect of the DHA-laxatives, danthrone, rhein, aloe-emodin and sennidine, on colorectal tumour cells. In SW480 carcinoma cultures, dose-dependent induction of urokinase secretion into the medium was the predominant effect. Simultaneously, cell numbers were decreased by DHA-aglycones, but not by sennoside or the biphenylic laxative bisacodyl. DNA synthesis was not similarly reduced: 0.4-4 microM danthrone and sennidine even stimulated 5-bromo-2'-desoxyuridine (BrdU) uptake into DNA. When uptake was normalised to cell number, danthrone and sennidine doubled BrdU uptake/10(6) cells, 18 microM rhein and 0.7 microM aloe-emodin induced increases of 37 and 50%, respectively. This may at least partially be due to selective resistance of S-phase cells to DHA-caused cell loss. In VACO235 adenoma cells, sennidine and aloe-emodin did not affect urokinase secretion, but stimulated growth. Both cell numbers and DNA synthesis were increased. In contrast to SW480 carcinoma cells, VACO235 cells were also sensitive to sennoside and bisacodyl. No effects of DHA were observed in normal colorectal epithelial cells. The biological effects were preceeded by specific phosphorylation of cellular proteins with molecular weights of 110, 78, 63, 57 kDa, indicating the specific induction of a cellular signalling cascade by the laxatives.

Anthraquinones↗
PubMed1998

A surface active protein involved in aerial hyphae formation in the filamentous fungus Schizophillum commune restores the capacity of a bald mutant of the filamentous bacterium Streptomyces coelicolor to erect aerial structures.

The filamentous bacterium Streptomyces coelicolor undergoes a complex process of morphological differentiation involving the formation of a dense lawn of aerial hyphae that grow away from the colony surface into the air to form an aerial mycelium. Bald mutants of S. coelicolor, which are blocked in aerial mycelium formation, regain the capacity to erect aerial structures when exposed to a small hydrophobic protein called SapB, whose synthesis is temporally and spatially correlated with morphological differentiation. We now report that SapB is a surfactant that is capable of reducing the surface tension of water from 72 mJ m-2 to 30 mJ m-2 at a concentration of 50 microgram ml-1. We also report that SapB, like the surface-active peptide streptofactin produced by the species S. tendae, was capable of restoring the capacity of bald mutants of S. tendae to erect aerial structures. Strikingly, a member (SC3) of the hydrophobin family of fungal proteins involved in the erection of aerial hyphae in the filamentous fungus Schizophyllum commune was also capable of restoring the capacity of S. coelicolor and S. tendae bald mutants to erect aerial structures. SC3 is unrelated in structure to SapB and streptofactin but, like the streptomycetes proteins, the fungal protein is a surface active agent. Scanning electron microscopy revealed that aerial structures produced in response to both the bacterial or the fungal proteins were undifferentiated vegetative hyphae that had grown away from the colony surface but had not commenced the process of spore formation. We conclude that the production of SapB and streptofactin at the start of morphological differentiation contributes to the erection of aerial hyphae by decreasing the surface tension at the colony surface but that subsequent morphogenesis requires additional developmentally regulated events under the control of bald genes.

Bacterial Proteins↗
PubMed1998

[Appearance of choroidal melanoma on high resolution MRI using 1.5T with a dedicated surface coil in 200 consecutive patients].

PURPOSE: Choroidal melanomas usually present a characteristic appearance in MRI. Differing characteristics can cause problems in differential diagnosis between melanomas and other masses in the globe. The purpose of this study was to evaluate the appearance of choroidal melanomas with MRI in a large consecutive patient group. METHODS: In a prospective study, 200 patients with choroidal melanomas were investigated with MRI using a 1.5 T scanner and a 5 cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. RESULTS: 78.5% of the melanomas presented with homogeneous signal intensities within the tumor due to a homogeneous pigmentation whereas 21.5% of the melanomas demonstrated a mixed pigmentation. Signal intensities of the homogeneous melanomas in the plain T1-WI were moderately or markedly hyperintense compared to the vitreous in 29.3% and moderately or markedly hypointense in the T2-WI in 37.1%. An accompanying retinal detachment was found in 65.5% and an extraocular growth in 7.0%. CONCLUSIONS: In 10% to 37% we observed the typical well known MR appearance, including homogeneous high signal in the T1-WI and low signals in the T2-WI. For further differentiation, morphological criteria (e.g. shape, size, and position) were used, which are also discussed.

Choroid Neoplasms↗
PubMed1998

Human endothelin-converting enzyme-1 beta mRNA expression is regulated by an alternative promoter.

The central step in endothelin biosynthesis is site-specific cleavage of big endothelins by endothelin-converting enzymes (ECEs). ECE-1 is a membrane-bound metalloprotease, predominantly but not exclusively expressed in endothelial cells. ECE-1 is expressed in two mRNA isoforms, termed alpha and beta, which differ only in the 5'-terminal regions but are functionally very similar when expressed in vitro. The structure of the human ECE-1 gene suggests either alternative splicing or alternative promoters as underlying mechanisms of mRNA isoform expression. We have previously shown that the alpha-upstream region exerts promoter activity in endothelial cells. To clarify whether the 5'-untranslated region upstream of exon 3, which contains the beta-specific sequence, acts as an alternative transcriptional promoter, we sequenced and cloned 1,206 bp upstream of the beta-specific translation initiation codon in a luciferase reporter vector. After transfection, we detected strong promoter activity in primary cultured endothelial cells (HU-VECs, BAECs) but only marginal activity in the endothelial cell line ECV304 and in CHO cells. Maximal promoter activity was observed with the full-length construct, 1206 (136% of the SV40 promoter activity in BAECs). Transfection of serial deletion mutants indicated at least three major regulatory regions within the promoter. Our results are consistent with cell type-restricted action of the beta-promoter and, in conjunction with the previously reported transcriptional start sites, clearly prove the existence of an alternative beta-specific promoter located in intron 2 of the human ECE-1 gene.

Animals↗
PubMed1998

Endothelial expression of endothelin-converting enzyme-1 beta mRNA is regulated by the transcription factor Ets-1.

Cleavage of big endothelins (ETs) by endothelin-converting enzymes (ECEs) represents the final step in the biosynthesis of ETs. ECE-1 is expressed predominantly in endothelial cells and exists in two isoforms, termed alpha and beta, differing in their 5' termini. We have recently shown that isoform-specific mRNA expression is directed by alternative promoters. To investigate possible mechanisms of transcriptional regulation of ECE-1, we stimulated E.A. hy 926 cells with phorbol ester and found a greater than threefold increase in ECE-1 beta mRNA at 12-24 h of stimulation. Because the beta-specific promoter is characterized by multiple consensus sequences for transcription factors of the ETS family, Ets-1 and PEA3, we also analyzed Ets-1 mRNA expression and found at least a fivefold increase in Ets-1 mRNA at 3 h of phorbol ester stimulation. Gel shift analysis revealed a specific interaction of nuclear proteins isolated from E.A. hy 926 cells with an oligonucleotide harboring the Ets-1 consensus sequence. Using a specific anti-Ets-1 antibody, we detected a supershifted band indicating the expression of Ets-1 protein in E.A. hy 926 cells. We conclude that Ets-1 is involved in transcriptional upregulation of ECE-1 beta mRNA in E.A. hy 926 cells induced by phorbol ester.

Aspartic Acid Endopeptidases↗
PubMed1998

Fetal ECG extraction with nonlinear state-space projections.

We describe a method to suppress maternal and noise contaminations in single-lead fetal ECG recordings. A nonlinear state space projection technique originally developed for noise reduction in deterministically chaotic signals is used. The method is successfully applied to recordings with fetal components and noise of comparable amplitude.

Electrocardiography↗
PubMed1998

Poisoning with tilidine and naloxone: toxicokinetic and clinical observations.

The opioid analgesic tilidine and its metabolites were detected by high performance liquid chromatography (HPLC) with UV-detection in serum from a 28 year-old woman who ingested 100 ml Valoron (o)N containing 6.94 g of tilidine and about 0.56 g of naloxone with suicidal intention. Data on the toxicokinetics of tilidine in severe poisonings are missing. Therefore we followed serum concentrations of tilidine and metabolites for 48 or 96 h and for the first time calculated basic kinetic parameters in a massive life threatening poisoning. Serum concentration of tilidine 3 h after ingestion was 38.1 mg/l which is about 70 times of the upper therapeutic level in man and about ninefold above toxic concentrations known so far. The concentration of nortilidine, the primary active metabolite at this time was 18.8 mg/l. The terminal elimination half life's of tilidine and nortilidine were explicit, prolonged with 23.9 and 13.9 h respectively. The competitive opiate antagonist naloxone, which is added as a part of the industrially produced preparation Valoron N solution to minimise oral abuse is not able to prevent ventilatory depression in massive overdoses.

Adult↗